1. Field of the Invention
The present invention relates to a metal ion coordinated complex crystal which is suitable for use as light-polarizing particles for a light-adjusting component of a light valve or a light-adjusting glass, and which is composed of a cation of a nitrogen-containing heterocyclic aromatic compound, an anion of triiodine and a metal ion.
2. Description of the Related Art
Conventionally, one light-adjusting component performs its function by dispersing light-polarizing particles into a dispersion medium, and making them orient in the dispersion medium in response to an electric field. Another light-adjusting component has a function of controlling optical properties (light-transmitting and light-screening performance) of the dispersion medium by randomizing the light-polarizing particles in it. It is proposed in Japanese Unexamined Patent Publication No. 144893/1978 that a complex compound such as dihydrocinchonidine periodide compound is used as light-polarizing particles. When the light-polarizing particles are used for a light-adjusting component, a dispersion medium containing the light-polarizing particles is filled between a pair of transparent electrodes coating inner surface of a pair of transparent substrates. The dispersion medium may be filled into a micro cell in order to improve optical properties or safety of the light-adjusting component.
The above-mentioned dispersion medium containing the light-polarizing particles usually contains moisture. The molecules of water destroy a clathlate structure of a complex such as above-mentioned periodide compound, and resultantly polarizability of the dispersion deteriorates. However, the conventional light-polarizing particles have poor moisture resistance. A light-polarizing particle with excellent moisture resistance has to be developed in order to obtain durability and stability of a light-adjusting component.
As automobiles have been improved their performance, it is desired that a windshield glass can screen a light. Therefore, it is necessary to manufacture a light-screening glass using light-polarizing particles. When a light-screening glass is formed of a light-adjusting component comprising the above-described light-polarizing particles, a dispersion medium containing the light-polarizing particles should be sealed between a laminated glass in the middle stage of manufacturing the laminated glass. However, the light-polarizing particles deteriorate or decompose when they are exposed to a temperature above 100.degree. C. Therefore, the light-polarizing particles are not suitable for use as the laminated glass for automobiles which is produced at a temperature above 130.degree. C.
Thus, in case that the light-adjusting component is used for outer parts of automobiles or outer materials of houses, the light-adjusting component exposes to a more severe condition. As a result, it is required to use light-polarizing particles which have more excellent durability than conventional ones. In order to obtain a long-lived light-adjusting component, it is required to provide a complex crystal which shows excellent heat resistance, excellent moisture resistance and excellent insolubility.
In order to meet the above conditions, the present inventors previously filed Japanese Patent Application (Japanese Unexamined Patent Publication No. 17473/1993 and Japanese Unexamined Patent Publication No. 357199/1992) concerning heat resistant herapathite as a complex crystal which can be used as red light-polarizing particles. Subsequently, the inventors filed Japanese Patent Application (Japanese Patent Application No. 329115/1991, Japanese Patent Application No. 325592/1992 and Japanese Patent Application No. 187020/1992) concerning phenanthroline compound, which is tricyclic fused compound having a nitrogen atom as a fused ring member for blue light-polarizing particles. The complex crystal such as phenanthroline compound has the same effect as that of the complex crystal such as herapathite. However, if it is required to use a complex crystal which have further durability and heat resistance, the above complex crystal of phenanthroline compound are not enough to satisfy such durability and weather resistance.